热老化对核电主管道Z3CN20.09M不锈钢点蚀性能的影响

采用极化曲线和电化学交流阻抗法研究了400℃长期热老化对压水堆核电站一回路主管道用Z3CN20.09M铸造奥氏体不锈钢点蚀性能的影响.结果显示，材料的点蚀击破电位和电荷转移电阻随着热老化时间的延长而降低.热老化材料经550℃退火处理1 h后的点蚀击破电位和电荷转移电阻值均恢复到未老化材料的水平.研究表明此时α'相已经回溶，G相仍然存在，导致热老化试样点蚀性能下降的主要原因是α'相的析出.

Effect of thermal aging on the pitting corrosion of Z3CN20.09M stainless steel for primary coolant pipes of nuclear power plants

The effect of thermal aging at 400℃ for a longer time on the pitting corrosion of Z3CN20.09M cast austenite stainless steel (CASS) which is widely used in the primary coolant pipes of nuclear power plants was investigated by potentiodynamic anodic polarization and electrochemical impedance spectroscopy (EIS). The results show that the pitting potential and charge transfer resistance of the steel decrease with the increase of thermal aging time. It is interesting to note that the pitting potential and charge transfer resistance of specimens aged first and then annealed at 550℃ for 1 h increase up to those of the unaged. The results confirm that Cr-rich α' phase is dissolved in ferrite after annealing, but G phase still exists in ferrite at the same time, indicating that α' phase precipitated in ferrite is the main reason for the deterioration in pitting corrosion resistance of the thermally aged Z3CN20.09M steel.